An integrated circuit (IC) die may be disposed in a package to support the die, as well as to aid in forming electrical connections between the die and a next-level component, such as a motherboard or other circuit board. The package typically includes a substrate to which the die is both mechanically and electrically coupled. For example, the IC die may be coupled to the substrate by an array of interconnects in a flip-chip arrangement, with a layer of underfill disposed around the interconnects and between the die and substrate. Each of the interconnects may comprise a solder bump disposed on a terminal (e.g., bond pad, copper pillar, etc.) of the die that is attached by a solder reflow process to a mating terminal (e.g., pad, pillar, etc.) on the substrate. Alternatively, by way of further example, the IC die may be attached to the substrate by a layer of die attach adhesive, and a plurality of wire bonds may be formed between the die and substrate.
The IC die is disposed on one side of the substrate, and a number of electrically conductive terminals are formed on an opposing side of the substrate. The terminals on the opposing side of the substrate will be used to form electrical connections with the next-level component (e.g., a circuit board), and these electrical connections can be used to deliver power to the die and to transmit input/output (I/O) signals to and from the die. The electrically conductive terminals on the substrate's opposing side may comprise an array of pads (or lands, pillars, etc.) to which solder bumps have been attached, and these solder bumps may be electrically coupled to a corresponding array of pads (or other terminals) on the circuit board by a reflow process.
For some types of integrated circuit devices, the I/O requirements are increasing with each design generation. Even with reductions in the pitch (e.g., the distance between adjacent interconnects), larger package substrates are needed in some instances to accommodate the increased I/O (e.g., to provide greater surface area upon which interconnects can be formed). However, as the substrate increases in size, the potential for warpage also rises. It is known to place a stiffener on the upper, or die-side, of the package substrate, but the decrease in compliance provided by the stiffener increases the risk of shock-related failures.